Tests

Update capi_version for mypyc tests to 3.8 #14238

Job	Run time
Test suite with py39-ubuntu, mypyc-compiled	18m 12s
Test mypyc suite with 32-bit Python	7m 14s
Test suite with py39-windows-64	20m 26s
Test suite with py310-ubuntu	16m 48s
Test suite with py311-ubuntu, mypyc-compiled	16m 15s
Test suite with py312-ubuntu, mypyc-compiled	18m 0s
Test suite with py313-ubuntu, mypyc-compiled	18m 22s
mypyc runtime tests with py39-macos	5m 12s
Type check our own code (py39-ubuntu)	1m 50s
Type check our own code (py39-windows-64)	2m 11s
Formatting and code style with Black + ruff	57s
	2h 5m 27s

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